package path;

import java.util.ArrayList;
import java.util.Collections;

/**
 * A path finder implementation that uses the AStar heuristic based algorithm to
 * determine a path.
 * 
 */
public class AStarPathFinder {
	/** The set of nodes that have been searched through */
	private ArrayList<Node> closed = new ArrayList<Node>();
	/** The set of nodes that we do not yet consider fully searched */
	private SortedList open = new SortedList();

	/** The map being searched */
	private GameMap map;
	/** The maximum depth of search we're willing to accept before giving up */
	private int maxSearchDistance;

	/** The complete set of nodes across the map */
	private Node[][][] nodes;
	/** True if we allow diaganol movement */
	// private boolean allowDiagMovement;
	/** The heuristic we're applying to determine which nodes to search first */
	private ClosestHeuristic heuristic;

	/**
	 * Create a path finder with the default heuristic - closest to target.
	 * 
	 * @param map
	 *            The map to be searched
	 * @param maxSearchDistance
	 *            The maximum depth we'll search before giving up
	 * @param allowDiagMovement
	 *            True if the search should try diaganol movement
	 */
	public AStarPathFinder(GameMap map, int maxSearchDistance) {
		this(map, maxSearchDistance, new ClosestHeuristic());
	}

	/**
	 * Create a path finder
	 * 
	 * @param heuristic
	 *            The heuristic used to determine the search order of the map
	 * @param map
	 *            The map to be searched
	 * @param maxSearchDistance
	 *            The maximum depth we'll search before giving up
	 * @param allowDiagMovement
	 *            True if the search should try diaganol movement
	 */
	public AStarPathFinder(GameMap map, int maxSearchDistance,
			ClosestHeuristic heuristic) {
		this.heuristic = heuristic;
		this.map = map;
		this.maxSearchDistance = maxSearchDistance;
		// this.allowDiagMovement = allowDiagMovement;

		nodes = new Node[map.getLevels()][map.getWidthInTiles()][map
				.getHeightInTiles()];
		for (int f = 0; f < map.FLOORS; f++)

			for (int x = 0; x < map.getWidthInTiles(); x++) {
				for (int y = 0; y < map.getHeightInTiles(); y++) {
					nodes[f][x][y] = new Node(x, y, f);
				}
			}
	}

	/**
	 * @see PathFinder#findPath(Mover, int, int, int, int)
	 */
	public Path findPath(UnitMover mover, int sx, int sy, int tx, int ty,
			int op, int f) {
		// easy first check, if the destination is blocked, we can't get there
		// System.out.println("path finder con destination" + tx +ty);
		/*
		 * if (map.blocked(mover, tx, ty, op, f)) {
		 * System.out.println("hay caminos, bloqueado" + tx+ ty + "nel piano"
		 * +f); return null; }
		 */

		// initial state for A*. The closed group is empty. Only the starting
		// tile is in the open list and it's cost is zero, i.e. we're already
		// there
		nodes[f][sx][sy].cost = 0;
		nodes[f][sx][sy].depth = 0;
		closed.clear();
		open.clear();
		open.add(nodes[f][sx][sy]);

		nodes[f][tx][ty].parent = null;

		// while we haven't found the goal and haven't exceeded our max search
		// depth
		int maxDepth = 0;
		while ((maxDepth < maxSearchDistance) && (open.size() != 0)) {

			// pull out the first node in our open list, this is determined to
			// be the most likely to be the next step based on our heuristic
			Node current = getFirstInOpen();
			if (current == nodes[f][tx][ty]) {
				break;
			}

			removeFromOpen(current);
			addToClosed(current);

			// search through all the neighbours of the current node evaluating
			// them as next steps
			for (int x = -1; x < 2; x++) {
				for (int y = -1; y < 2; y++) {
					if ((x != 0) && (y != 0)) {
						continue;
					}

					// determine the location of the neighbour and evaluate it
					int xp = x + current.x;
					int yp = y + current.y;

					if (isValidLocation(mover, sx, sy, xp, yp, op, f)) {
						// the cost to get to this node is cost the current plus
						// the movement
						// cost to reach this node. Note that the heursitic
						// value is only used
						// in the sorted open list
						float nextStepCost = current.cost
								+ getMovementCost(mover, current.x, current.y,
										xp, yp, f);
						Node neighbour = nodes[f][xp][yp];
						map.pathFinderVisited(xp, yp, f);

						// if the new cost we've determined for this node is
						// lower than
						// it has been previously makes sure the node hasn't
						// been discarded. We've
						// determined that there might have been a better path
						// to get to
						// this node so it needs to be re-evaluated
						if (nextStepCost < neighbour.cost) {
							if (inOpenList(neighbour)) {
								removeFromOpen(neighbour);
							}
							if (inClosedList(neighbour)) {
								removeFromClosed(neighbour);
							}
						}

						// if the node hasn't already been processed and
						// discarded then
						// reset it's cost to our current cost and add it as a
						// next possible
						// step (i.e. to the open list)
						if (!inOpenList(neighbour)
								&& !(inClosedList(neighbour))) {
							neighbour.cost = nextStepCost;
							neighbour.heuristic = getHeuristicCost(mover, xp,
									yp, tx, ty);
							maxDepth = Math.max(maxDepth,
									neighbour.setParent(current));
							addToOpen(neighbour);
						}
					}
				}
			}
		}

		// since we've got an empty open list or we've run out of search
		// there was no path. Just return null
		if (nodes[f][tx][ty].parent == null) {
			return null;
		}

		// At this point we've definitely found a path so we can uses the parent
		// references of the nodes to find out way from the target location back
		// to the start recording the nodes on the way.
		Path path = new Path();
		Node target = nodes[f][tx][ty];
		while (target != nodes[f][sx][sy]) {
			path.prependStep(target.x, target.y);
			target = target.parent;
		}
		path.prependStep(sx, sy);

		// thats it, we have our path
		// System.out.println("path" + path.getLength());
		return path;
	}

	
	/**
	 * @see PathFinder#findPath(Mover, int, int, int, int)
	 */
	public Path findPartialPath(UnitMover mover, int sx, int sy, int tx, int ty,
			int op, int f) {
		// easy first check, if the destination is blocked, we can't get there
		// System.out.println("path finder con destination" + tx +ty);
		/*
		 * if (map.blocked(mover, tx, ty, op, f)) {
		 * System.out.println("hay caminos, bloqueado" + tx+ ty + "nel piano"
		 * +f); return null; }
		 */

		// initial state for A*. The closed group is empty. Only the starting
		// tile is in the open list and it's cost is zero, i.e. we're already
		// there
		nodes[f][sx][sy].cost = 0;
		nodes[f][sx][sy].depth = 0;
		closed.clear();
		open.clear();
		open.add(nodes[f][sx][sy]);

		nodes[f][tx][ty].parent = null;

		// while we haven't found the goal and haven't exceeded our max search
		// depth
		int maxDepth = 0;
		while ((maxDepth < maxSearchDistance) && (open.size() != 0)) {

			// pull out the first node in our open list, this is determined to
			// be the most likely to be the next step based on our heuristic
			Node current = getFirstInOpen();
			if (current == nodes[f][tx][ty]) {
				break;
			}

			removeFromOpen(current);
			addToClosed(current);

			// search through all the neighbours of the current node evaluating
			// them as next steps
			for (int x = -1; x < 2; x++) {
				for (int y = -1; y < 2; y++) {
					if ((x != 0) && (y != 0)) {
						continue;
					}

					// determine the location of the neighbour and evaluate it
					int xp = x + current.x;
					int yp = y + current.y;

				
					if (isValidLocation(mover, sx, sy, xp, yp, op, f)) {
						// the cost to get to this node is cost the current plus
						// the movement
						// cost to reach this node. Note that the heursitic
						// value is only used
						// in the sorted open list
						float nextStepCost = current.cost
								+ getMovementCost(mover, current.x, current.y,
										xp, yp, f);
						Node neighbour = nodes[f][xp][yp];
						map.pathFinderVisited(xp, yp, f);

						// if the new cost we've determined for this node is
						// lower than
						// it has been previously makes sure the node hasn't
						// been discarded. We've
						// determined that there might have been a better path
						// to get to
						// this node so it needs to be re-evaluated
						if (nextStepCost < neighbour.cost) {
							if (inOpenList(neighbour)) {
								removeFromOpen(neighbour);
							}
							if (inClosedList(neighbour)) {
								removeFromClosed(neighbour);
							}
						}

						// if the node hasn't already been processed and
						// discarded then
						// reset it's cost to our current cost and add it as a
						// next possible
						// step (i.e. to the open list)
						if (!inOpenList(neighbour)
								&& !(inClosedList(neighbour))) {
							neighbour.cost = nextStepCost;
							neighbour.heuristic = getHeuristicCost(mover, xp,
									yp, tx, ty);
							maxDepth = Math.max(maxDepth,
									neighbour.setParent(current));
							addToOpen(neighbour);
						}
					}
				}
			}
		}

		// since we've got an empty open list or we've run out of search
		// there was no path. Just return null
		if (nodes[f][tx][ty].parent == null) {
			return null;
		}

		// At this point we've definitely found a path so we can uses the parent
		// references of the nodes to find out way from the target location back
		// to the start recording the nodes on the way.
		Path path = new Path();
		Node target = nodes[f][tx][ty];
		while (target != nodes[f][sx][sy]) {
			path.prependStep(target.x, target.y);
			target = target.parent;
		}
		path.prependStep(sx, sy);

		// thats it, we have our path
		// System.out.println("path" + path.getLength());
		return path;
	}

	/**
	 * Get the first element from the open list. This is the next one to be
	 * searched.
	 * 
	 * @return The first element in the open list
	 */
	protected Node getFirstInOpen() {
		return (Node) open.first();
	}

	/**
	 * Add a node to the open list
	 * 
	 * @param node
	 *            The node to be added to the open list
	 */
	protected void addToOpen(Node node) {
		open.add(node);
	}

	/**
	 * Check if a node is in the open list
	 * 
	 * @param node
	 *            The node to check for
	 * @return True if the node given is in the open list
	 */
	protected boolean inOpenList(Node node) {
		return open.contains(node);
	}

	/**
	 * Remove a node from the open list
	 * 
	 * @param node
	 *            The node to remove from the open list
	 */
	protected void removeFromOpen(Node node) {
		open.remove(node);
	}

	/**
	 * Add a node to the closed list
	 * 
	 * @param node
	 *            The node to add to the closed list
	 */
	protected void addToClosed(Node node) {
		closed.add(node);
	}

	/**
	 * Check if the node supplied is in the closed list
	 * 
	 * @param node
	 *            The node to search for
	 * @return True if the node specified is in the closed list
	 */
	protected boolean inClosedList(Node node) {
		return closed.contains(node);
	}

	/**
	 * Remove a node from the closed list
	 * 
	 * @param node
	 *            The node to remove from the closed list
	 */
	protected void removeFromClosed(Node node) {
		closed.remove(node);
	}

	/**
	 * Check if a given location is valid for the supplied mover
	 * 
	 * @param mover
	 *            The mover that would hold a given location
	 * @param sx
	 *            The starting x coordinate
	 * @param sy
	 *            The starting y coordinate
	 * @param x
	 *            The x coordinate of the location to check
	 * @param y
	 *            The y coordinate of the location to check
	 * @return True if the location is valid for the given mover
	 */
	protected boolean isValidLocation(UnitMover mover, int sx, int sy, int x,
			int y, int option, int f) {
		boolean invalid = (x < 0) || (y < 0) || (x >= map.getWidthInTiles())
				|| (y >= map.getHeightInTiles());
		//System.out.println("invalid" + invalid);
		if ((!invalid) && ((sx != x) || (sy != y))) {
			// if(map.getTerrain(x, y, f)== GameMap.DOOR)
			// return true;
			invalid = map.blocked(mover, x, y, option, f);
		}

		return !invalid;
	}
	
	
	protected boolean isValidLocation2(UnitMover mover, int sx, int sy, int x,
			int y, int option, int f) {
		boolean invalid = (x < 0) || (y < 0) || (x >= map.getWidthInTiles())
				|| (y >= map.getHeightInTiles());
		//System.out.println("invalid" + invalid);
		if ((!invalid) && ((sx != x) || (sy != y))) {
			// if(map.getTerrain(x, y, f)== GameMap.DOOR)
			// return true;
			invalid = map.blocked(mover, x, y, 2, f);
		}

		return !invalid;
	}

	/**
	 * Get the cost to move through a given location
	 * 
	 * @param mover
	 *            The entity that is being moved
	 * @param sx
	 *            The x coordinate of the tile whose cost is being determined
	 * @param sy
	 *            The y coordiante of the tile whose cost is being determined
	 * @param tx
	 *            The x coordinate of the target location
	 * @param ty
	 *            The y coordinate of the target location
	 * @return The cost of movement through the given tile
	 */
	public float getMovementCost(UnitMover mover, int sx, int sy, int tx,
			int ty, int f) {
		return map.getCost(mover, sx, sy, f, tx, ty, f);
	}

	/**
	 * Get the heuristic cost for the given location. This determines in which
	 * order the locations are processed.
	 * 
	 * @param mover
	 *            The entity that is being moved
	 * @param x
	 *            The x coordinate of the tile whose cost is being determined
	 * @param y
	 *            The y coordiante of the tile whose cost is being determined
	 * @param tx
	 *            The x coordinate of the target location
	 * @param ty
	 *            The y coordinate of the target location
	 * @return The heuristic cost assigned to the tile
	 */
	public float getHeuristicCost(UnitMover mover, int x, int y, int tx, int ty) {
		return heuristic.getCost(map, mover, x, y, tx, ty);
	}

	/**
	 * A simple sorted list
	 * 
	 * @author kevin
	 */
	private class SortedList {
		/** The list of elements */
		private ArrayList list = new ArrayList();

		/**
		 * Retrieve the first element from the list
		 * 
		 * @return The first element from the list
		 */
		public Object first() {
			return list.get(0);
		}

		/**
		 * Empty the list
		 */
		public void clear() {
			list.clear();
		}

		/**
		 * Add an element to the list - causes sorting
		 * 
		 * @param o
		 *            The element to add
		 */
		public void add(Object o) {
			list.add(o);
			Collections.sort(list);
		}

		/**
		 * Remove an element from the list
		 * 
		 * @param o
		 *            The element to remove
		 */
		public void remove(Object o) {
			list.remove(o);
		}

		/**
		 * Get the number of elements in the list
		 * 
		 * @return The number of element in the list
		 */
		public int size() {
			return list.size();
		}

		/**
		 * Check if an element is in the list
		 * 
		 * @param o
		 *            The element to search for
		 * @return True if the element is in the list
		 */
		public boolean contains(Object o) {
			return list.contains(o);
		}
	}

	/**
	 * A single node in the search graph
	 */
	public class Node implements Comparable {
		/** The x coordinate of the node */
		private int x;
		/** The y coordinate of the node */
		private int y;
		/** The f level coordinate of the node */
		// private int f;

		/** The path cost for this node */
		private float cost;
		/** The parent of this node, how we reached it in the search */
		private Node parent;
		/** The heuristic cost of this node */
		private float heuristic;
		/** The search depth of this node */
		private int depth;
		private int f;

		/**
		 * Create a new node
		 * 
		 * @param x
		 *            The x coordinate of the node
		 * @param y
		 *            The y coordinate of the node
		 */
		public Node(int x, int y, int f) {
			this.x = x;
			this.y = y;
			this.f = f;
		}

		/**
		 * Set the parent of this node
		 * 
		 * @param parent
		 *            The parent node which lead us to this node
		 * @return The depth we have no reached in searching
		 */
		public int setParent(Node parent) {
			depth = parent.depth + 1;
			this.parent = parent;

			return depth;
		}

		/**
		 * @see Comparable#compareTo(Object)
		 */
		public int compareTo(Object other) {
			Node o = (Node) other;

			float f = heuristic + cost;
			float of = o.heuristic + o.cost;

			if (f < of) {
				return -1;
			} else if (f > of) {
				return 1;
			} else {
				return 0;
			}
		}
	}
}
